The present invention relates to LED-based lighting systems and, in particular, traffic signals. The exemplary embodiments find particular application in conjunction with minimizing reflection of light received from an outside source, such as the sun. One approach is to utilize one or more retroreflectors to reflect the externally originating light back toward the source. Another approach is to use a lens to direct externally originating light into an aperture within the signal housing.
Automotive, railway, vehicular, waterway, illumination, and/or pedestrian signals are employed to regulate motorists and pedestrians via various commands. These commands are provided by an illumination source with particular colors and/or shapes that are each associated with an instruction. For example, light emitting diodes can illuminate an appropriate signal that indicates a command to motorists and/or pedestrians.
In order to provide a signal that is clearly visible, signals can locate the light elements on a reflective substrate and further use reflectors to direct light emitted from the illumination source. A common problem with traffic signals occurs when external light (e.g., from the sun) enters the front of the signal, is reflected off internal specular surfaces and exits the signal at an angle that reaches a driver's and/or pedestrian's eyes.
The problem can be exacerbated by one or more optical element utilized to direct the light from the illumination source out of the signal. In general, light generated by the illumination source is directed out of the signal via optical elements, such as a lens, a collimator, a diffuser and the like. However, the same components can direct externally originating light into the signal following substantially the same path. In this manner, light that is received from an external source is directed toward the illumination element typically located at the back of the signal. The externally originating light can then be further reflected by the reflective substrate and out the signal on the same path as light generated by the illumination source light. In this manner, it can appear that the signal is on, even when the illumination source is unit.
Accordingly, it would be advantageous to have systems and methods which minimize reflection of light received by a signal from an outside source.